This invention relates to a liposoluble antioxidant mixture based on an organic acid.
The advantage of presenting antioxidant organic acids in a liposoluble form is due to the fact that they have an inhibiting effect on the oxidation of lipids in biological systems. In combination with vitamin E, vitamin C, for example, has a synergistic antioxidant effect because, as a reducing agent, L-ascorbic acid converts the tocopheroxyl derivatives into tocopherols which are capable of refixing the free radicals in the form of tocopheroxyl derivatives.
Hydrophilic L-ascorbic acid can be made liposoluble by esterification of its hydroxyl groups in the 5 or 6 position with a fatty acid. Thus, 6-O-palmitoyl-L-ascorbic acid or ascorbyl palmitate is used as an additive for protecting fats against oxidation and also as a source of vitamin C. However, this compound has the disadvantage of dissolving very slowly in fats at temperatures at which they are not degraded. Accordingly, it has been necessary to add partial glycerides or complex lipids, for example soya lecithin. Even with these additives, however, the incorporation of ascorbyl palmitate at a level guaranteeing an adequate antioxidant effect can only be carried out at a relatively high temperature of the order of 130.degree. C. for a certain time, for example 30 minutes, which induces degradation of the fats and the antioxidant itself, which has a melting point of 115.5.degree. C.
European patent application European Patent Application O 0 326 829, for example, relates to the production of a liposoluble antioxidant mixture containing ascorbic acid which is solid at room temperature, and which is based on polar lipids, such as lecithins. A mixture such as this may readily be used in dry solid products. However, its incorporation in oils rich in heat-sensitive polyunsaturated fatty acids requires the use of a polar solvent, for example ethanol, which has to be subsequently eliminated. In addition, its incorporation in products containing water, for example emulsions, is problematical because, in the presence of water, ascorbic acid has a tendency to cause degumming of lecithin which has an adverse effect on their stability.
In addition, according to U.S. Pat. No. 2,432,698 for example, vitamins A and B can be protected against oxidation by addition of niacinamide. In cases where these vitamins have to be stabilized with an oil as support, optionally in the presence of tocopherol, it is necessary according to this patent to add natural solvents, such as ethyl and lauric alcohols, for example, to the mixture as niacinamide is not liposoluble.